public void TestPush()
        {
            IFancyCalculator x = new FancyCalculator();
            var stack          = x.GetStack();

            x.Push(45);
            Assert.IsTrue(stack.Count == 1);
            Assert.IsTrue(stack.Contains(45));
        }
        public void TestClear()
        {
            IFancyCalculator x = new FancyCalculator();
            var stack          = x.GetStack();

            x.Push(25);
            x.Push(45);
            Assert.IsTrue(stack.Count == 2);
            x.Clear();
            Assert.IsTrue(stack.Count == 0);
        }
        public void TestAdd()
        {
            IFancyCalculator x = new FancyCalculator();
            var stack          = x.GetStack();

            Assert.IsTrue(stack.Count == 0);
            x.Push(10);
            x.Push(20);
            x.Push(30);
            x.Push(40);
            x.Add();
            Assert.IsTrue(x.Top() == 70);
        }
        public void TestMultiply()
        {
            IFancyCalculator x = new FancyCalculator();
            var calc           = x.GetStack();

            Assert.IsTrue(x.Size() == 0);
            x.Push(10);
            x.Push(20);
            x.Push(30);
            x.Push(40);
            x.Multiply();
            Assert.IsTrue(x.Top() == 1200);
            x.Multiply();
            Assert.IsTrue(x.Top() == 24000);
        }
        public void TestSize()
        {
            IFancyCalculator x = new FancyCalculator();
            var stack          = x.GetStack();

            x.Push(25);
            Assert.AreEqual(stack.Count, x.Size());
            Assert.AreEqual(x.Size(), 1);
            x.Push(25);
            Assert.AreEqual(stack.Count, x.Size());
            Assert.AreEqual(x.Size(), 2);
            x.Push(25);
            Assert.AreEqual(stack.Count, x.Size());
            Assert.AreEqual(x.Size(), 3);
        }